OLNEY, TEXAS: Texas witnessed a disturbing case of murder in 2019 when an unsuspecting high school teacher and mother of four, Manuela Allen, was tragically attacked in her own home without her family's knowledge.

The identity of the attacker, then-18-year-old Julius Mullins, was a shock to the community. What complicates the case even more is that Mullins formerly dated Allen's daughter and had ambiguous motivations for taking her life.

NBC's true crime show 'Dateline' is delving into this mysterious murder in their upcoming episode, 'The Footprint at the Lake', aiming to uncover the truth. The episode is scheduled to air on October 13, Friday, at 9 pm.

How was Manuela Allen killed?

On the night of July 6, 2019, a then-unidentified individual entered the Allen residence and assaulted Manuela in her own bedroom. The primary evidence of suspicion was the blood found all over their house, notably on the bedroom floor. It indicated significant blood loss that could have only resulted in death.

While this attack should have definitely alerted the family, none of them had heard any sounds as they remained plugged into devices that could shut the noises out.

When the Allen family - Manuela's husband Peter, daughter Kiara, and brother Darian - woke up the following day, they were shocked to discover her absence. All that remained were traces of blood and the murder weapon, a knife.

In addition to Manuela's disappearance, her SUV was also missing, initially leading the family to think she may have driven herself to the hospital. However, the significant amount of blood suggested a more ominous turn of events, prompting police involvement.

Shortly after, her car was found near Lake Cooper, and nearby, Manuela's body was discovered wrapped in sheets, according to CBS News.

Who killed Manuela Allen?

It did not take long for the police to zero in on the killer.

While they suspected it was someone who closely knew the high school teacher because of their ability to navigate through Allens' home and take away the SUV, Peter provided a lead that led them to the actual perpetrator.

Peter urged the investigators to interview a delinquent teenager, who then pointed them toward Julius Mullins, Kiara's ex-boyfriend. Julius was later confirmed as a suspect when his bike's tire tracks matched those found at the crime scene near the lake, as reported by News Channel 6.

Julius had a troubled background and a history of disturbing behavior at school. Initially, he denied the murder allegations and even attempted to shift blame onto Peter. However, mounting evidence ultimately compelled him to confess to the murder of Manuela.

In the upcoming 'Dateline' episode, exclusive interviews with Julius will shed further light on the details surrounding Manuela's tragic murder.